IsoimmunizationErythroblastosis Fetalis

Hemolytic Disease of the Newborn

Zeev Weiner

Director of Ultrasound in Obstetrics and Gynecology

Lutheran Medical Center

Rh Isoimmunization

Rh Blood Group System:

Cc

Dd

Ee

40 other antigens: Du, Cw,….

The D antigen

In 85% the D antigen is present

55% heterozygous

Sensitization occurs during blood transfusion and during pregnancy

The D antigen

Isoimmunization is dose dependent

0.1 ml is sufficient

ABO incompatibility confers partial protection!

Obstetrical risks for Rh isoimmunization

Abortions (2-5%) – How early?

Pregnancy and delivery (1.6%)

Procedures: Amniocentesis

Trauma

Rh Hemolytic Disease

Mild: Fetal anemia with Hb>12-13g/dl.

No sonographic findings.

Rh Hemolytic Disease

Moderate: Fetal anemia with Hb between 7-12 g/dl

Possible sonographic findings.

Rh Hemolytic Disease

Severe: Anemia with Hb < 7g/dl

Most of the time there are sonographic findings

Monitoring the sensitization

When do we check anti-D titers? At the beginning, 28 wks, after birth

What is a significant titer?Above 1:8-1:16

How accurate are the titers?……..

What is the meaning of very low titers and do we have to give prophylaxis?

…….

Follow-up patients with sensitization

Checking the Rh antigens of the father if negative no need to

follow-up?

Checking the Rh antigens of the fetus if negative definitely no need to

follow-up

Follow-up patients with Rh isoimmunization

Follow-up can start at 18 weeks gestation

There are 3 options:

Amniocentesis

Cordocentesis

Doppler

Amniocentesis for patients with Rh isoimmunization

The Liley or the modified curves.

Advantage: less complicated procedure

Disadvantage: delta OD may not accurately correlate with the anemia

Cordocentesis for patients with Rh isoimmunization

Blood sampling from the umbilical vein, hepatic or portal veins,

intracardiac

Advantage: more reliable, immediate option for treatment

Disadvantage: higher risk

Doppler studies for patients with Rh isoimmunization

Peak velocity of the middle cerebral artery (why not other vessels?)

Advantage: non invasive

Disadvantage: correlation with anemia is still questionable

Treatment of Fetal Anemia

Indication: Hb < 10-11 g/L (Hct<30) or fetal hydrops

Technique: Intraperitoneal, Intravascular (umbilical vein or

others), Intracardiac

Treatment of Fetal Anemia

Irradiated O- packed red cells (Hct=0.85-0.9)

V =[(Hct-f - Hct-i)xEFWx120]: Hct-d

Guidelines for repeat transfusion: 1% decline per day, Hct=25

Treatment of Severe Cases of Rh Isoimmunization

Early transfusions starting at 16-18 wks

A weekly high-dose of IVIG between 13-18 wks

AID

Time and Mode of Delivery

33-34 wks with documented lung maturity

34-36 weeks with no need to document lung maturity

No indication for a CS

Prevention of Rh Isoimmunization

300 micrograms of Anti-D Ab

At 28 wks and within 72 hrs postpartum

Protect against 15 ml of RBC

Other Common antibodies Causing Isoimmunization

Kell

C

E